The present invention relates to an apparatus for inserting connection yarns into a three-dimensional fabric, and more particularly to an apparatus for simultaneously inserting a plurality of connection yarns into a fiber lamination. Specifically, the apparatus is used to manufacture a fiber lamination that is folded in at least two directions and has connection yarns that extend perpendicularly to each layer of the lamination.
Japanese Unexamined Patent Publication No. 8-218249 discloses a method for manufacturing a three-dimensional fabric. In this method, pins are provided with a predetermined pitch between one another on a frame to surround an area where connection yarns are inserted into a fiber lamination. Fiber layers are formed by folding back fibers at each pin to form a lamination. A row of insertion needles insert connection yarns, which are perpendicular to the lamination, into the lamination.
Connection yarns are typically inserted into a lamination in the following manner. A frame holding the lamination is first secured to a support table. The support table is moved by a predetermined pitch such that the lamination passes the movement range of connection yarn insertion needles. When insertion of the connection yarns in a predetermined area of the lamination is completed, the frame, together with the lamination, is removed from the support table. Then, another table to which a lamination is attached is fixed to the support table. Connection yarns are then inserted into the new lamination.
When inserting connection yarns into a lamination, a row of first needles, to each of which a connection yarn is engaged, are inserted into the lamination. After the needles penetrate the lamination and the needle eyes are located at the opposite side of the lamination from the standby position of the insertion needles, the needles are slightly retracted. This forms a yarn loop at the distal end of each insertion needle at the opposite side of the lamination. A second needle to which a lock yarn is engaged is reciprocated such that the lock yarn is inserted into each loop. The first needles are pulled back in this state, which tightens the lamination and prevents the connection yarns from being loosened. The second needle has a latch at its distal end and is reciprocated by a driving device. The driving device is generally an air cylinder or a lead screw mechanism, which is actuated by a servomotor.
Three-dimensional fabrics are typically used to form a frame member of a composite. The strength of such composite largely depends on the properties of the three-dimensional fabric. To increase the strength of the composite, the density of the fiber (lines) in the fabric must be increased and the lines must be orderly. Accordingly, laminations must be tightly bundled by connection yarns and the tightening force of the connection yarns must be equalized.
Japanese Unexamined Patent Publication No. 10-325043 discloses a connection yarn supplying apparatus having a tension adjusting means and a brake means. The tension adjusting means includes two stationary rollers and a movable roller. The stationary rollers are located at predetermined positions and are perpendicular to the inserting direction of the connection yarns. The movable roller is supported by a pivotable support arm and is parallel to the stationary rollers. The support arm is actuated by an air cylinder. the connection yarn is bent and held between the stationary rollers and the movable roller. To control the tension of a connection yarn, the brake means is first activated. The air cylinder then applies a force in a predetermined direction to the support arm to tension the connection yarn. The tension of the connection yarn is controlled by adjusting the pressure of air in the air cylinder.
A three-dimensional fabric may be manufactured by inserting connection yarns into a lamination that is supported only by a frame. However, the process of inserting and removing needles is likely to loosen the fibers of the lamination, which degrades the characteristics of the material when a composite is formed from the lamination. The apparatus of the publication No. 8-218249 has an apparatus for overcoming this drawback. That is, the apparatus of the publication has first and second pressing members to sandwich a lamination in the vicinity of the inserting area of the row of first needles. Connection yarns are inserted into the lamination while the pressing members are holding the laminate. The first and second pressing members are moved between an operation position and a standby position. When at the operational position, the pressing members hold the lamination. When at the standby position, the pressing members do not engage the laminate.
A three-dimensional fabric with high density is obtained by setting the pitch of the connecting yarns to three millimeters. Therefore, if the length of a lamination is sixty centimeters and the pitch of the connection yarns is three millimeters, there will be two hundred insertion cycles. The above described apparatuses include air cylinders and lead screw mechanisms. A lead screw mechanism is actuated by a servomotor. The first needles, the position of which must be relatively accurately determined, and the second needle, which is moved by a relatively great distance, are actuated by lead screw mechanism. The tension adjusting means and first and second pressing members, which requires a pressure control, are actuated by air cylinders.
However, if an air cylinder is used for moving a member, it is difficult to increase the moving speed while maintaining the applied pressure. While inserting connection yarns into a lamination, the pressing members must be separated from the lamination when the lamination is moved by a predetermined pitch. When moving the lamination by the predetermine pitch, the separation distance between the lamination and the pressing members may be a minimum distance. However, since the lamination is secured to the frame by the support pins, if the pressing members are retracted by the minimum distance when setting the frame on a predetermined position of the yarn inserting apparatus, the pins interfere with the pressing members. Therefore, the standby position of the pressing members is separated from the lamination such that the pressing members do not interfere with the support pins. As a result, the moving distance of the pressing members is increased, which extends the time required for inserting connection yarns. Accordingly, productivity is lowered.
The movable roller of the tension adjusting means for connection yarns is supported by the support arm. The support arm is actuated by an air cylinder. The support arm therefore cannot be moved quickly, which also lowers productivity.
The apparatuses of the publications can process only be one frame of lamination at a time. Therefore, the insertion of connection yarns must be prepared every time a new frame is set in the apparatus. Specifically, the end of each connection yarn, which is inserted in the corresponding first needle, must be fixed to the frame, which increases the time required for manufacturing three-dimensional fabric. Productivity is lowered accordingly.
The second needle for a lock yarn is actuated by the lead screw mechanism, which is actuated by a servomotor. The moving speed of the lock yarn needle is therefore not as fast as desired. Thus, there is a demand for a lock yarn needle that moves faster to improve productivity.